The present invention relates to a navigation system. More particularly, the invention relates to a method of and system for navigating a killer vehicle near an underwater mine emitting a magnetic field. The invention uses measurements of the mine's magnetic field, supplied by two magnetic sensors affixed to the killer vehicle, to calculate the relative position of the killer vehicle from the mine.
In modern conflict, the ability to quickly find and destroy sea mines can be of great importance. One concept considered for ferrous-cased mines involves the use of two autonomous underwater vehicles (AUVs). The first AUV acts as a hunter vehicle which detects and classifies the mine using both sonar and magnetic sensors. The magnetic sensors determine the mine's position and both the magnitude and direction of the mine's magnetic moment. (The magnetic moment is a well known vector quantity which characterizes the magnetic source strength and the magnetic oreintation of a magnetized object.) Additionally, the hunter vehicle carries multiple second AUVs, or killer vehicles.
The killer vehicle functions like a mini-torpedo. After launch from the hunter vehicle, the killer vehicle anchors itself near the mine at a spot pre-determined by the hunter vehicle. After a delay that allows the hunter vehicle to leave the area, the killer vehicle moves towards the mine in order to destroy it.
One serious problem with this concept is providing the killer vehicle with accurate navigation information as it attempts to maneuver towards the mine and destroy it. The hunter vehicle has determined the mine's position within a certain error tolerance. Similarly, the killer vehicle has reached its intended anchor point within another error tolerance. If the killer vehicle uses the hunter vehicle's estimate of the mine's position and simple dead reckoning to navigate to the mine, these two sources of error (plus additional error sources such as the strength of unknown currents) may prevent the killer vehicle from passing close enough to the mine to destroy it. Moreover, since the killer vehicle is carried by the hunter vehicle, its warhead must be small and lightweight. Thus, an accurate placement of the killer vehicle's warhead near the casing of the mine may be required in order to ensure destruction. The more accurate the navigation system, the smaller the killer vehicle's warhead can be made thus saving weight. This, in turn, would either increase the endurance of the hunter vehicle or permit it to carry more payload including, possibly, more killer vehicles.
An active sonar could provide the necessary navigational information but would be more expensive and require more electrical power than the present invention.